1. Field of the Invention
The present invention relates to the fatty acid esterification of propoxylated glycerin and to improved recovery of fatty acids from various vapor streams found in the system.
2. Description of the Prior Art
The preparation of esters of propoxylated polyols is known. A particularly important technology relates to the preparation of food grade quality esters of propoxylated glycerin as described, for example, in U.S. Pat. Nos. 4,983,329, 5,571,935, 5,681,939, and the like.
During the esterification reaction water is formed which must be removed in order to achieve high esterification conversion. Generally water removal is accomplished by stripping water of reaction from the esterification reactor by nitrogen stripping and/or by carrying out the reaction under vacuum conditions.
A certain amount of fatty acid is volatilized and removed with the water of reaction which causes problems in recovery procedures by virtue of the high melting point of the volatilized fatty acid. The high melting fatty acids tend to solidify on cold condensation surfaces causing severe heat transfer problems.
Similarly, the esterification reaction mixture, upon completion of the desired esterification, contains unreacted fatty acid which must be stripped from the ester. Problems are also encountered in the recovery of the stripped fatty acid due to the high fatty acid meeting point.